In recent years, some mobile terminals such as cellular phones include a touch panel, touch switch, or other such touch sensor for an input device, such as an operation unit or switches, that detects an operation by a user. Input devices provided with a touch sensor are in wide use apart from mobile terminals as well, in information devices such as calculators or ticket vending machines, household appliances such as microwave ovens, televisions, or lighting appliances, industrial devices (factory automation equipment), and the like.
A variety of types of such touch sensors are known, such as a resistive film type, capacitive type, optical type, or the like. All of these types of touch sensors, however, simply detect contact by a finger, stylus pen, or the like. Upon being contacted, the touch sensor itself is not physically displaced like a push-button switch.
Accordingly, even if an operation by contact is recognized by the input device, the operator cannot receive any feedback for the operation. Therefore, the operator operating the touch sensor obtains no sense of operation such as that obtained when pushing a key or button constituted by a push-button switch. As a result, a problem exists in that the operator has no way of knowing that the contact operation has been properly recognized by the input device unless the input device starts a predetermined process in accordance with the contact on the touch sensor.
To address this problem, a method has been proposed to provide feedback that is neither auditory nor visual by vibrating the touch sensor upon the touch sensor detecting contact (for example, see Patent Literature 1 and Patent Literature 2).